A controlling method called intermittent control is known as one example of control to control components in an information processing device to be activated or stopped as necessary to reduce power consumption of the entire information processing device.
As one example of the intermittent control, a method in which a central processing unit (CPU) generates descriptor information that is information on input/output of transfer data and an input unit and an output unit refer to the descriptor information to control input/output of transfer data is known.
According to this control method, the CPU can stop operating after generation of the descriptor information and before generation of the next descriptor. In addition, the input unit stops operating after referring to the descriptor information and storing the transfer data into a buffer memory until the next transfer data arrives. The output unit is activated at a time point when writing of the transfer data into the buffer memory is finished, refers to the descriptor information and outputs the transfer data written in the buffer memory.
If the intermittent control is performed on the input and output units, the CPU generates descriptor information each time an event of input/output processing (such as reception of a frame from a network) occurs. There is thus a disadvantage that the throughput decreases since the/overhead on the CPU operation increases in proportion to the frequency of events of input processing.
Moreover, because the CPU is stopped in order to increase the effect of reduction in power consumption, the CPU has to be restarted for generating descriptor information or for other operations, and furthermore, the operating system, the middleware and the like have to be restored as necessary. In this case, there is a disadvantage that the overhead significantly increases.
To the contrary, it can be considered not to perform the intermittent control on the CPU since the likelihood that the throughput is decreased becomes higher if the CPU is stopped. In this case, however, there is a disadvantage that the intermittent control has limited effects in reducing power consumption because the CPU continues operating.